12-14-2017, 01:30 PM
Hi Greg,
As per your pm I took a look at the schematic, boy it's got a lot of squiggly lines!!!!
Would start with cleaning the sockets and switches w/contact cleaner. Loctal sockets can be trouble in terms of poor connections. 7X7 is sort of a red herring (I think) it's the fm det and 1st audio and that seem to be ok. In terms of troubleshooting one way is to go thru and ground the control grid of each stage (this stops the signal from the previous stage from enter the next). Caps it the plate circuit are suspect like micas. Breaking out the signal tracer and listening for noise at the grid and plate. Sometimes this can backfire if the noise gets into the avc circuit then it can be picked in thru all of the tube that are connected to it. Years ago use to use freeze spray but don't know if you can still get it (Freon). Would start off focusing in on the 7F8 area.
GL
As per your pm I took a look at the schematic, boy it's got a lot of squiggly lines!!!!
Would start with cleaning the sockets and switches w/contact cleaner. Loctal sockets can be trouble in terms of poor connections. 7X7 is sort of a red herring (I think) it's the fm det and 1st audio and that seem to be ok. In terms of troubleshooting one way is to go thru and ground the control grid of each stage (this stops the signal from the previous stage from enter the next). Caps it the plate circuit are suspect like micas. Breaking out the signal tracer and listening for noise at the grid and plate. Sometimes this can backfire if the noise gets into the avc circuit then it can be picked in thru all of the tube that are connected to it. Years ago use to use freeze spray but don't know if you can still get it (Freon). Would start off focusing in on the 7F8 area.
GL
When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got!
Terry
